Effects of composition of mannitol salt agar on identification of Staphylococcus aureus

Abstract

ObjectiveTo explore the effects of sodium chloride and tryptone in the components of mannitol salt agar on the quality of mannitol salt agar， and investigate the product quality of 5 domestic brands and 1 imported brand of mannitol salt agar sold on the market.MethodsThe effects of sodium chloride and tryptone with different brands and concentrations of sodium chloride and tryptone on the quality of mannitol salt agar were investigated using plate coating counting and semi quantitative scoring method. Quantitative determination of the growth of different types of Staphylococcus aureus and Escherichia coli on 5 domestic brands and 1 imported brand of mannitol salt agar. Referring to GB 4789.28—2013， the growth rate， growth index， and colony size of different brands of culture media for different strains were compared， and the quality of each brand of culture media was evaluated.ResultsThere were significant differences in the growth rate and growth index of experimental strains on mannitol salt agar prepared with different types and concentrations of sodium chloride or tryptone. The growth index of non target bacteria in different brands of mannitol salt agar was qualified， but there were significant differences in the growth rate and colony size of the target bacteria.ConclusionSodium chloride and tryptone have a significant impact on the quality of mannitol salt agar， which directly determines whether the medium is qualified. There are significant differences in the quality of different brands of mannitol salt agar sold domestically and internationally， and the quality of domestic mannitol salt agar is better than that of imported medium.

Keywords

• staphylococcus aureus
• escherichia coli
• mannitol salt agar
• sodium chloride
• tryptone
• the quality control